Fractured upper 4th premolar and Fractured lower canine
Dogs fracture (break) teeth in many ways. Fractured canine teeth (fangs) and incisors (small teeth in front of and between the fangs) usually result from either an impact with a solid object, from tugging behavior, or from fights. Fractured upper 4th premolars (largest upper chewing tooth in the cheek area) or lower first molars are from chewing hard or inappropriate objects such as real bones, rocks, horse/cow hooves, and even some chew toys such as hard plastic or nylon bones or other hard toys. Fractures of the upper 4th premolars are very common type of dental fractures that we see in dogs. In addition, fractured teeth with pulp exposure are often not recognized to be the serious problem that they are. Taking a “watch and see what happens” approach to a fractured tooth is not appropriate, because the vast majority of pain and damage to the pet’s body are not visible to the naked eye with this condition.
A tooth consists of 3 parts: enamel, dentin, and pulp. The enamel is the tough non-porous outer coating of the tooth that is normally the only part of the tooth that can be seen. The dentin is a more porous bony material that lies beneath the enamel, and is softer than enamel. The dentin has microscopic tubules present, which normally allow nutrients to diffuse from the pulp into the dentin, to keep the tooth structures alive and healthy. In addition, the dentinal tubules contain the nerve endings that supply sensation to the teeth. Animals have approximately 50,000-100,000 dentinal tubules per square millimeter of tooth surface, which is about twice the amount than humans have. Therefore, when the dentin is exposed to the mouth, there is significant sensitivity and the tubules are large enough to potentially allow bacteria to work their way into the tooth, and into the pulp itself. The pulp consists of the blood vessels and nerves that supply both nutrients and sensation to the tooth.
Consequences of tooth fracture:
If the tooth fracture has resulted in exposure of the pulp, and the time between fracture and dental treatment is greater than 48 hours, or is unknown, then it is safe to assume that bacteria have invaded the pulp tissue. When bacteria invade the pulp tissue, it results in inflammation of the pulp tissue, called pulpitis. This causes irreversible damage and swelling of the pulp, which ultimately results in the death of the pulp tissue (pulp necrosis), and therefore, death of the tooth. If the pulp becomes necrotic (dead), it becomes a place to harbor bacteria from the bloodstream, which can result in abscessation. In addition, it becomes a source of chronic pain, as well as allowing leakage of the necrotic contents of the pulp into the system. The rare circumstance wherein the tooth fracture has occurred less than 48 hours before treatment is addressed below.
In the majority of cases, there are only 2 options. We must either do root canal therapy or extract the tooth. When we do root canal therapy on a fractured tooth, we either make an opening in the enamel to allow access to the inside of the tooth or, in some cases, use the fracture site itself to access the inside of the tooth. Then, we remove the necrotic pulp from inside the tooth, seal the end of the root, and fill the pulp chamber with an inert material. Then, we do a composite restoration, or “filling” in the tooth, to seal it from exposure to the bacteria in the oral cavity.
Root canal therapy vs. extraction:
X-ray of tooth after root canal
The advantages of root canal therapy are that we keep this tooth as a functional tooth in the mouth and maintain a more normal appearance to the mouth. Certain teeth have more critical functions than others. The large premolars and molars are important chewing teeth and assist in side-to-side stabilization of the jaw, the canines help with gripping large objects and are important for the structure of the mouth, and the incisors are used for fine gripping.
The disadvantages of root canal therapy are the following: there is increased cost of a root canal over extraction, follow-up x-rays are required, and that there is a small chance of failure. With root canal therapy, we need to take anesthetized dental x-rays 9-12 months after the procedure, to make sure the procedure was successful. There are a small number of these procedures that will not be successful. If root canal therapy fails, additional treatment will be needed at additional cost. The treatment could include: re-cleaning and filling of the root canal, a less involved surgical procedure called an apicoectomy, or extraction.
As for extraction, the advantages are that it is a one step procedure and that it is less expensive than root canal therapy. The disadvantages are that we lose the functional and structural benefits of the affected tooth, and there are a small percentage of extractions that can develop complications. In some cases, complicating factors (such as periodontal disease or young teeth that have not fully developed their root structure) are present that make the long-term prognosis for the affected tooth very poor. In these cases root canal therapy is not an option, due to the increased chance of failure of the procedure, and extraction becomes the only reasonable option.
If root canal therapy is performed, as discussed above, crown placement is an optional additional procedure. Crowns are also used to strengthen teeth that have become weakened due to excessive wear (usually from chronic chewing). Crown placement is the procedure of manufacturing and placement of an artificial tooth over the existing tooth structure.
Composite restoration vs. crown restoration
After root canal therapy, there are 2 options for completion of the procedure, composite restoration or crown placement:
1) Composite restoration.
Tooth with composite restoration
Composite restoration is the placement of a filling in the opening through which the root canal procedure was performed. The filling seals the pulp chamber and canal to help prevent bacteria in the mouth from invading the tooth and causing the root canal procedure to fail.
The advantages of a composite filling are that it is done in a single procedure at the time of the root canal therapy, and it does not add significant cost to the root canal therapy. The disadvantages of a composite filling are that it does not restore any of the normal tooth structure, and there is a slightly higher possibility of the root canal failing due to microscopic leaks in the filling, allowing bacteria to enter the tooth.
2) Crown placement.
Tooth with crown
Crown placement is the process of placing a manufactured metal or ceramic artificial tooth over the existing tooth structure that has been compromised. The process of placing a crown is a 2-step procedure. The first step is performed at the same time as the root canal therapy. It involves shaping the tooth to receive the crown and making impressions of the tooth that will be used by the dental laboratory to manufacture a metal or ceramic crown specifically made to fit the tooth. In the second anesthetic procedure, which is performed about 1-2 weeks later, the manufactured crown is cemented in place and any final adjustments are made.
Crown placement is most beneficial for teeth that will be subject to significant forces, such as chewing. Therefore, crown placement is strongly recommended in most cases where an upper 4th premolar or lower first molar has been fractured.
The advantages of crown placement are that it re-creates the tooth function and some of the structure, and that it has the least likely chance of the root canal procedure failing due to microscopic leakage of bacteria into the tooth. The disadvantages of crown placement are that it requires 2 separate anesthetic procedures to perform and that it is more expensive than simple composite restoration. Lastly, it is also important to note that there is a small percentage chance that crowns can fail, as well. In rare cases, the crown can loosen or come off of the tooth. If a crown fails, it is more common for the crown to stay attached to the tooth and the tooth to be fractured below where the crown is placed.
One feature of crown placement in animals that could be considered either an advantage or disadvantage is that the most crowns used in animals are made of metal. Therefore, the manufactured crown that is placed is silver in color, rather than the color of a natural tooth. The porcelain crowns that are routinely used in people are too susceptible to breakage when used in animals, and therefore carry a higher risk of failure in the long run.
Fresh tooth fracture (less than 48 hours old):
If the timing of the tooth fracture is known for certain (not the time that the fractured was discovered, but the time that it actually occurred) and the patient can be safely anesthetized within 48 hours of the occurrence of the fracture, there is a procedure called vital pulpotomy that is an option. In this procedure, some of the pulp is removed, a pulp dressing is placed, and a composite filling is placed in the tooth. The goal is to maintain the living tissues inside the tooth in a healthy state. One study showed that if a vital pulpotomy is performed within 48 hours of tooth fracture, that there is an 88% chance of success. However, if the procedure is performed after 48 hours, but before 1 week has passed, the success rate drops to 50%. If a vital pulpotomy is performed, then follow up anesthetized dental x-rays should be taken every 6 months for at least 2 years to confirm the success of the procedure. If the procedure should fail, then root canal therapy or extraction would need to be performed. In most cases where there is a fractured tooth, root canal therapy is preferred over vital pulpotomy as the first line of treatment.
Tooth after vital pulpotomy and X-ray of tooth at left
Tooth fracture without pulp exposure:
If the tooth fracture has resulted in dentin exposure only, with no pulp exposure, the result is a tooth that is more sensitive to heat, cold, pressure, drying, and certain foods. There is also potential for bacteria to invade the pulp via the exposed dentinal tubules. If bacteria invade the pulp tissue, it results in inflammation of the pulp tissue, called pulpitis. This causes irreversible damage and swelling of the pulp, which ultimately results in the death of the pulp tissue (pulp necrosis). If the pulp becomes necrotic (dead), it becomes a great place to harbor bacteria from the bloodstream, which can result in abscessation. In addition, it becomes a source of chronic pain, as well as allowing leakage of the necrotic contents of the pulp chamber into the blood stream.
The best way to determine if a tooth has become non-vital (dead) is by taking dental x-rays to evaluate the affected tooth. Dental x-rays are taken under anesthesia in animals. Therefore, we will not know if the affected tooth is living or not, until we are performing the treatment procedure. In addition, there is a slight possibility that a tooth that has recently become infected or dead will not show changes on x-rays yet, because these changes take time to appear.
Treatment options for fracture without pulp exposure:
In the case of exposed dentin in a tooth that appears to be living, there are four treatment options:
1) Crown placement (see notes on crown placement above). This is the best option to both protect the tooth and restore full function.
2) Composite restoration. This is also a very effective approach for these teeth. Composite restoration is the placement of a filling material over the defect in the tooth. This will permanently seal the exposed dentinal tubules and will both eliminate sensitivity as well as greatly reduce the chance of bacterial invasion into the tooth. In addition, the results are more aesthetically pleasing than with dentin bonding only.
Also, be aware that if bacterial invasion has already occurred, but the tooth has not become devitalized or abscessed yet, then the tooth will still progress to become a non-vital tooth, even if we do a composite restoration. If bacteria have invaded the tooth, but are not causing problems yet, then there is no way to detect this. This is one of the risks of this procedure. Also be aware that the composite restoration can be broken off, just like the original tooth enamel was broken, especially if the pet continues the behavior that caused the tooth to fracture in the first place (such as chewing rocks or a cage door).
3) Dentin bonding. This is the application of a sealing material to the exposed dentin, in order to seal the dentinal tubules. The goal is to reduce sensitivity and reduce the chance of bacterial invasion through the dentinal tubules. This is simpler and less expensive than composite restoration, but does not improve the appearance of the tooth. At one time it was thought that this was a temporary procedure that was probably effective for 6-12 months, and should be repeated annually. However, current studies indicate that it probably is an effective long-term treatment for dentin exposure. As a precaution, it is still prudent to repeat the dentin bonding each time a pet is under anesthesia for a dental procedure.
4) Fluoride treatment. Home treatment with stannous fluoride can help to strengthen the dentin and reduce sensitivity, and does not require anesthesia. This is the most conservative treatment for exposed dentin, and should be applied weekly, or as directed.
Exact estimate for the cost of treatment for a fractured tooth will vary depending upon the specific tooth that is affected, the treatment option chosen, and other circumstances surrounding the procedure. Estimates are given on a case-by-case basis. In addition, treatment options may change based on anesthetized exam and x-rays of the affected tooth.